An examination of the role of dopamine systems in reward with particular concentration on the mesolimbic dopamine system is proposed. The primary objective is to localize in the monkey a dopamine containing intracranial self-stimulation (ICSS) system by characterizing it anatomically and pharmacologically. Rhesus monkeys (Macaca mulatta) will be implanted with multiple electrode and cannula arrays at several locations varying from the mesodiencephalic junction to the forebrain. ICSS responsiveness will be mapped anatomically and baseline ICSS behavior will be manipulated with the drugs known to lock and facilitate dopamine metabolism by local intracranial injections of the drugs into projection areas of the mesolimbic system. Finally a preliminary experiment will attempt to measure actual endogenous release of dopamine during an ICSS session. Results will contribute to our knowledge of neuroanatomical and neurochemical systems implicated in disturbances of affect and behavior disorders.